10 Pitfalls of Sink Replacement

Replacing a kitchen sink and faucet is a quick way to give your kitchen a new look, but there are potential plumbing and installation problems to watch out for. This article explains how to avoid the ten most common.

Got your eye on a deeper sink? Measure the tailpiece first!

Measure the tailpiece

You can choose a new sink with a deeper basin than the existing sink has, but if it hangs down too low, it won't drain properly and you'll have to lower the sanitary tee connection in the drain line inside the wall. You'll definitely want to avoid this task if the connection is metal and ends up being behind base cabinets. Plastic pipe is easier—if you can get to it easily. The actual tee connection may be several studs over from where the waste arm enters the wall.

Measure the sink tailpiece between the basket strainer and the tee. That measurement is the extra depth that can be added to the sink bowl without lowering the drainpipe going into the wall. Also be aware that a new disposer may have a lower drainpipe
than your existing one—but it can't be
lower than the tee. If the disposer drainpipe
will be too low, consider a sink with different depth
bowls. You'll have a deep bowl for dishes and a shallow
one for the disposer.

Make sure the new sink will cover the old hole

Check the cutout size

A sink that's too small for the
countertop opening will leave
ugly gaps along the sides (or even
fall right through the hole!). Before removing
the existing sink, measure the opening
from underneath. Measure all four
sides because the cutout may not
be square. Pay special attention to
the corners. Contractors often cut
them at 90-degree angles (instead
of rounding them off) because it's faster.

Take the measurements with you when buying the
new sink and make sure it'll cover the opening, including
any square corners. If you can't find a sink that'll
fit, buy a larger one and enlarge the opening.

Swollen countertops spell trouble

Check for water stains

Leaks around a sink rim
can soak the particleboard
under a plastic
laminate countertop. A
little water damage is
normal and won't interfere
with your new sink.
But severe swelling will
prevent the new sink
from sitting flat on the
countertop. And crumbling
particleboard won't
provide a solid base for
the clips that fasten
the sink to the
countertop.

Look at the countertop
surface around
the sink. Check for bulges or areas where the laminate
has loosened from the particleboard. Then look at the countertop
from under the sink for areas that are too spongy to
support sink clips or support the sink itself. If you find any
of these problems, replace the countertop.

Seal with caulk, not putty

Use the right sealant

Plumber's putty has long
been the standard sealant
for sink baskets and
sometimes even sink
rims. The problem with
putty is that it eventually
dries out, cracks and
causes leaks. Worse, it
can damage some plastics, including some of the plastics used to make
sinks. Avoid drips and disasters by using a silicone caulk instead.

Use a kitchen-and-bath 100 percent silicone that requires solvent
cleanup—sold at home centers. Apply a bead around the sink
opening when you set in the sink and around the drain opening when you
set the disposer drain and basket strainer. Wipe away excess caulk.

Seal basket strainer

Seal around the drain opening with silicone caulk instead of plumber's putty when you
set the disposer drain and basket strainer. Wipe away excess caulk.

Remove ALL the old caulk

Use caulk remover

The caulk around your new sink is all that'll stand between your countertop and
water damage. For a lasting, watertight bond with the countertop, you have to completely
remove the old caulk.

Remove the old sink, then
scrape off the caulk (or
plumber's putty) with a putty
knife. Apply a caulk remover
(sold at home centers) to
stubborn caulk. Let the caulk
remover sit for a couple of
hours, then scrape off the
softened caulk. Finally, use
rubbing alcohol or nail polish
remover to wipe off residue,
and then clean the surface
with a sponge and water.

Get the gunk out

Flush out sediment

Working on the water lines always shakes sediment loose.
The last thing you want is for these deposits to clog
your new faucet. Avoid this problem by purging
the lines before hooking up the new supply lines.

Once the entire project is complete and the
new supply lines are attached to the faucet, fasten
the old supply lines to the shutoff valves. Next, turn
the water all the way on for a full minute to wash
away any debris in the lines. Then attach the
new lines to the shutoff valves. After three days,
take the aerator off the faucet and rinse away
any sediment that has seeped through.

Make sure you have enough holes

Match faucet to sink openings

Most sinks have three holes for the faucet and a fourth
for an accessory, such as a sprayer or a soap dispenser.
But some faucets require only one or two holes, and
you may not want enough accessories to use the rest.
You can buy plugs for unused holes, but they usually
don't match the sink. If the sink doesn't have enough
holes, cutting an extra hole in
stainless steel or cast iron is
often difficult or impossible.

To avoid these hassles, choose
the faucet and accessories first, then buy a
sink with a matching number of holes.
Some sinks have “knockouts” that you
can drill to provide extra holes. You
can also special-order a sink with the
number of holes you need.

Trash all the old parts

Replace the entire waste assembly

Resist the temptation to save a few bucks by
reusing the old drainpipes. The threads
are probably corroded and won't form a
tight connection. A new drain assembly
is easier to install and less
likely to leak.

Instead of shopping
for each individual
part for the drain, buy a
kit at a home center
that has everything you
need. A sink kit
includes drainpipes, fittings,
shutoff valves, supply
lines and new basket
strainers.

Test the shutoff valves first

Replace leaky valves

If the shutoff valves under your sink don't work or you don't have any, you'll have
to turn off the water supply to the entire house while replacing the sink. This
could cause domestic
strife, especially if the
job turns into a half day
or longer project, so
make sure the valves
work before going to the
home center.

To test the valves,
close them and turn on
the faucet. The faucet
may drip for a minute
or two, but if the drip
continues, the shutoff
valves are leaking. Repair
or replace old valves. If
you're buying new ones,
use quarter-turn balltype
shutoff valves.
They're more reliable
and less likely to leak at
the packing nut.

Rusty old pipe? Cheat!

Solve tough problems with couplings

Corroded steel drainpipes are a bear to work with,
since the slip nuts are almost impossible to loosen
or retighten. You can easily bypass those rusty old
threads by adding a section of plastic pipe.

If the slip nut attached to the drainpipe in the
wall won't come off, spray on WD-40 and try a bigger wrench. If that
doesn't work, cut off the drainpipe with a hacksaw (save as much of the
threaded area as possible). Then buy a plastic trap adapter, a transition
coupling and a piece of plastic pipe (PVC or ABS) and cement (sold at home centers). Cement the adapter to a 4-in. section of
pipe, then place the coupler over the other end of the pipe and over the
steel drainpipe.